In a structure made of reinforced concrete, such as a tunnel, a bridge, a building, a retaining wall, a dam, or a civil construction, in order to evaluate the strength or life or to determine construction procedure, it is needed to detect locations of reinforcing iron rods, diameters of reinforcing iron rods, the degree of corrosion of reinforcing iron rods, and/or adhesion strength of reinforcing iron rods, for the purpose of, for example, evaluation of strength or life of the structure or determination of procedure of construction. Various techniques for the above purpose are known. They include radiography for taking an X-ray image of a structure placed between an X-ray generator and a film, ultrasonic diagnosis in which an ultrasonic wave is generated by an ultrasonic generator placed on the surface of concrete and diagnosis/measurement is performed on the basis of detection of a reflected ultrasonic wave, a percussion method in which diagnosis/measurement is performed on the basis of an echo detected after tapping a surface of a structure with a hammer or the like, an infrared imaging method in which a surface of a structure is illuminated with an infrared ray, and a microwave method in which a surface of a structure is illuminated with a microwave.
However, the conventional methods of detecting locations of reinforcing iron rods or corrosion of reinforcing iron rods have problems as described below. For example, in radiography, it is needed to put a structure between the X-ray generator and the film, and thus this method has various limitations such as those on the shape, the size, and the location. This method cannot be substantially used for tunnels, dams, or the like. Another problem is that control is needed so as to prevent a human body from being significantly damaged by an X-ray and thus it is not easy to employ this method.
In the detection of the locations of reinforcing iron rods using the percussion method, a high skill is needed. Because detection is based on the skill, it is difficult to achieve high reliability in detection. When diagnosis of corrosion is performed using this method, corrosion cannot be easily detected unless reinforcing iron rods are so significantly corroded that a void is created. In this method, detection of corrosion is based on the skill and thus the reliability of detection is low. For this reason, it is needed to partially expose a reinforcing iron rod and visually observe an exposed part to confirm.
In the ultrasonic diagnosis method, an ultrasonic wave is applied to the surface of reinforced concrete, and the location of a reinforcing iron rod is determined from an ultrasonic wave reflected from the reinforcing iron rod. However, the concrete includes gravel and a large number of non-continuous parts created by bubbles or the like, which cause the ultrasonic wave to be attenuated or scattered and thus make it difficult to perform analysis.
In the infrared imaging method and also in the microwave method, because the infrared ray or the microwave is greatly attenuated by concrete, measurement is possible only in a region near the surface of a structure.
As a for a method of diagnosing corrosion, it is known to detect an acoustic wave generated by elastic energy released when a structure is deformed or cracked and analyze the detected acoustic wave to determine the degree of corrosion of the structure. This method is known as an acoustic diagnosis method. More specifically, an acoustic emission (AE) sensor is attached to a structure and the output of the AE sensor is monitored over a long period of time to detect an acoustic emission which occurs accidentally and suddenly due to stress corrosion cracking. However, it is needed to continuously perform measurement over a long period and it is also needed to apply an unnecessarily large load. Thus, this technique is not suitable for detection of corrosion of a structure.
As described above, no conventional method is known which allows high-reliability non-destructive detection of the degree of corrosion of reinforcing iron rods in reinforced concrete, adhesion strength between concrete and reinforcing iron rods, or the location or the diameter of a reinforcing iron rod in concrete. The lack of effective methods causes an error to occur in prediction of strength or life, and thus can cause an unpredictable disaster to occur.
In structures including a prestressed conductor and a non-conductive material covering the conductor, that is, structures made of prestressed-concrete, such as bridges, electric poles, and railroad ties, reinforcing iron rods prestressed so as to enhance their elasticity are embedded in concrete. When such a structure is used for a long period, there is a possibility that a reinforcing iron rod fractures. However, no conventional technique is known which allows such a fracture to be detected in a non-destructive fashion. Therefore, periodical replacement at scheduled intervals is needed, or otherwise an unpredictable disaster can occur.
In a civil engineering work or a construction work in which it is required to drive stakes into ground, it is necessary to know the locations of existing water pipes or gas pipes buried in the ground. In this case, water pipes and gas pipes are conductors embedded in a non-conductive material. Conventionally, a metal detector or sonar is used to determine the buried location. However, such an apparatus is complicated and special technical knowledge is needed to handle it. There is no technique which can be easily used to detect a precise location under ground. Thus, in many cases, a troublesome job, such as digging up the ground, is needed to make confirmation.
In the case of a structure including a plurality of conductors bound with each other via a binding member, such as a bridge constructed as a road by joining iron plates using bolts and nuts, for the purpose of safety, it is necessary to periodically examine whether bolts and nuts are maintained in a securely fastened state. However, in structures having a large size such as bridges, large bolts and nuts are used and they are fastened by very large torque. Therefore, it is impossible to manually diagnose using a torque wrench or the like, and diagnosis is performed using a dedicated machine having a large size. Another problem in such diagnosis is that it is necessary to close the bridge during the diagnosis.
In view of the above, a first object of the present invention is to provide an apparatus for diagnosing or measuring, non-destructively and precisely, a structure including a conductor and a non-conductive material covering the conductor in terms of the degree of corrosion, the adhesive strength, the cover depth, and the diameter of the conductor. A specific example is an apparatus for non-destructively diagnosing or measuring the degree of corrosion of reinforcing iron rods in reinforced concrete, the strength of adhesion between reinforcing iron rods and concrete, and/or the cover depth or the diameter of reinforcing iron rods in concrete.
A second object of the present invention is to provide an apparatus for non-destructively and precisely measuring the location of a concoctor in a structure including the conductor and a non-conductive material covering the conductor. A specific example is an apparatus for non-destructively and precisely measuring the location of reinforcing iron rods in reinforced concrete.
A third object of the present invention is to provide an apparatus for diagnosing or measuring, in detail, the degree of corrosion, the adhesion strength, and/or the location of a conductor in a structure including the conductor and a non-conductive material covering the conductor, on the basis of a distribution of small vibrations over the entire surface and a propagation mode of vibrations. A specific example is an apparatus for non-destructively diagnosing or measuring the degree of corrosion of reinforcing iron rods in reinforced concrete, the strength of adhesion between reinforcing iron rods and concrete, and/or the location of reinforcing iron rods in concrete.
A fourth object of the present invention is to provide a method of non-destructively and precisely diagnosing or measuring the degree of corrosion and/or the adhesion strength of a conductor in a structure including the conductor and a non-conductive material covering the conductor. A specific example is a method of non-destructively diagnosing or measuring the degree of corrosion of reinforcing iron rods in reinforced concrete and/or the strength of adhesion between reinforcing iron rods and concrete.
A firth object of the present invention is to provide a method of non-destructively and precisely measuring the location of a conductor in a structure including the conductor and a non-conductive material covering the conductor. A specific example is a method of non-destructively measuring the location of reinforcing iron rods in reinforced concrete.
A sixth object of the present invention is to provide a method of non-destructively and precisely measuring the location of a conductor in a structure including the conductor and a non-conductive material covering the conductor. A specific example is a method of non-destructively diagnosing or measuring, in detail, the degree of corrosion of reinforcing iron rods in reinforced concrete, the strength of adhesion between reinforcing iron rods and concrete, and/or the location of reinforcing iron rods in concrete, on the basis of a distribution of small vibrations over the entire surface and a propagation mode of vibrations.
A seventh object of the present invention is to provide a method of measuring the diameter or the cover depth of a conductor in a structure including the conductor and a non-conductive material covering the conductor. A specific example is a method of measuring the diameter or the cover depth of reinforcing iron rods in reinforced concrete.
An eighth object of the present invention is to provide a method of diagnosing or measuring whether conductors bound with each other via a binding member are in a state in which the conductors are securely bound by the binding member. A specific example is a method of diagnosing or measuring whether iron plates bound with each other via a bolt and a nut are in a state in which the iron plates are securely bound by the bolt and the nut.
A ninth object of the present invention is to provide a method of non-destructively and precisely diagnosing or measuring the location of a conductor embedded in a non-conductive material. A specific example is a method of diagnosing or measuring the location of a water pipe or a gas pipe buried under the ground.
A tenth object of the present invention is to provide a method of non-destructively and precisely diagnosing or measuring a structure including a conductor and a non-conductive material covering the conductor as to whether the conductor has a fracture. A specific example is a method of determining whether a bridge, an electric pole, or a railroad tie, which are made of prestressed concrete, has a fracture and/or measuring the location of such a fracture.